Method and apparatus for generating and detecting impulses



April 12, 1932. R. A. FESSENDEN 1, 9

METHOD AND APPARATUS FOR GENERATING AND DETECTING iMPULSES ori inalFiled March 2:5, 1918 ml Ill-a Patented Apr. 12, 1932 REGINALD A.rnssn'NmtN, or CHESTNUT HI'LL, mssacnosn'r'rs,

'assrenon. To sun- MABIN'E SIGNAL COMPANY, OF PORTLAND, A CORPORATION OF1":

Marne!) AND Arr'mrtrs roa GENERATING AND nnrrzcrme uns Originalapplication filed March 23, 1918, Serial No. 224,288. Patent No.1,501,105, dated July 15,1994.

Divided and this application flledjlay 21, 1924. Serial No. 714,889.

My invention relates to methods and apparatus for generating anddetecting impulses;

and more particularlv to producing electrical effects or impulses bymechanical means, and mechanical effects or impulses by electricalmeans; and still more particularly to the transmission and detection ofsounds, more especially telephonic, and phonographic sounds. 1osimplicity, accuracy,-freedom from disturbance, are itsfprincipalobjects.

Fig. 1 shows diagrammatically means for producing an electricalindication by mechanically straining a magnetic wire, the strain beingproduced by sound waves.

Fig. 2 shows diagrammatically means for producing a sound from a pianoby the reverse action, i. e. the creating of an-impulse or sound byelectrical means. It also shows the p means applied to a piano forproducing an electrical efl'ect by mechanical strain.

This application is a division, so far as the parts which are common, ofmy U. S. application Serial Number 224,288, filed March 23rd, 1918,Patent No. 1,501,105, issued July 15, 1924, and of my application SerialNumber 531,166; filed J an. 23rd, 1922, the latter a division of anearlier case. In Figure 1, 6 is a box having two opposite 3o ends formedof the diaphragms 7, 9. The

ends of a' wire 8 are attached to these diaphra'gmsr7, 9', and the wire8 is preferably made of some magnetic material, preferably very softiron or nickel. 11 is a magnetizlng' 85 coil for magnetizing the wire 8,and12 is a source of continuous current, though an alternating currentsource may be used. 10 is a second coil wound over the wire 8 andconcentric with 11 and the terminals of thewire 10 are connected withthe electric circuits as shown. 9

i 20 is a similar box, 19 being a similar wire,

and'21and 22 similar coils to 10 and 11, and

23 is a source of voltage similar to 12. As

ing but merely for balancing, diaphragms similar to 7 ,9, are omittedinthis box.

24 is a source of alternating current and A the alternating current fromthe upper brush flows up till it reaches the junction ofthe Increasedeificiency, convenience,-

1 through the medium in which the box is immuch trouble from atmosphericand disthis box is not used for sending and receiv-' primaries 14, 15,when it divides and one half flows-through the primary 14, the condenser13- and coil 10, and back again to the other brush of 24. The other halfflows through the primary 15, condenser 16, coil 21, to the other brush0f 24. v In operation the current from the/source 24 flows through thedivided circuits, and the. I primaries 14, 15 beingwound so as to actoppositely on the secondary 17, no current is produced in the secondary17 and. no sound 1n the telephone receiver 18, so longv as the twocircuits are balanced. Y

As soon, however, as

a sound travelling mersed strikes the diaphragms 9, 7, the wire 8 is putin vibration and its magnetism is al-' tered and the circuit is thrownout of balance and a sound is heard in the telephone receiver 1 76)While a simple form of magnetic detector is here shewn, I have foundthat any of the well known forms of magnetic detector used for wirelesstelegraphy, "for example those invented by applicant, may be usedprovided that they are re-arranged and their construction. so alteredthat the compressional waves to be detected set the magnetic circuit invi.- bration, and consequently I do not limit myself to this specificconstruction here shewn. I Applicants invention of the wirelesstelephone (Trans. Amer. Inst. Elect. Eng. July 1908 and U. S. Pat.706,747, Sept. 29th, 1901) has now come into extensive use, butat'present there is much distortion, both in the pick-up of thesounds'to be transmitted, at the sending station; and in the reroduction at the receiving station; and t ore is 90 turbing noises dueto other causes; the loudness of. the sound transmitted varies with theposition of the actors'on the stage, in vaudeville and otherperformances; and when reproduced the sound is loud close up to the loudspeaker and fainter at adistance,.in the ratio of thlsquare of thedistance; and there is an un-natural quality about the re-production. Inthe making and re-production of phonograph records sim- '100 than anyloud speaker now known to the art).

ilar difliculties are met with, except that in place of atmosphericthere is the scratching of the needle.

These, and other difliculties are overcome by applicants area source ofsound production shown in U. S. Patents No. 1,277,562, filed Feb. 28,1917, issued Sept. 3, 1918; No. 1,213,176, filed June 27, 1916, issuedJan. 23, 1917 No; 1,212,202, filed May 12, 1 916, issued Jan. 16, 1917No. 1,319,521, filed June 8, 1917, issued Oct. 20, 1919, and others, andmore especially by the forms shown and described herein and in anapplication divided herefrom and about to be filed.

In Fig. 2 one form is shewn. Here 40 is the sounding board of a piano,which is constructed in the usual manner, well known in the art, exceptthat between the tuning pegs 41, 42 there is stretched a nickel wire, orone of other magnetgizable material, 43. Upon this is wound a layer ofenameled copper wire, 44, so that the whole has the appearance of theordinary wound piano wire. 23 is a source of current, as before, and 45is a two way double pole switch for connecting 44 to the receiver whenit is desired to transmit the sounds emitted by the piano when playedupon in the usual manner; or for connecting to the transmitter when itis desired that the piano should act as a loud speaker (for applicanthas discovered that it is possible for a piano to so act, and better 1The tonogen type where, as shown in Fig. 2, the vibration is produced bythe lengthening and shortening of the nickel(or iron or othermagnetizable material) wire when its magnetization is altered by thetransmitter currents, is especially useful in the case of deaf orpartially deaf people, who can be made to hear when such a wire as shewnat 43, 44 of Fig. 2 is held between their teeth and transmitter currentspassed. The arm may be otherwise shaped if desired.

The vibration generating elements shewn in Figure 2 are convenientlyattachable,

as shown, to any musical instrument as- They may also be.

to a banjo, mandolin, etc. attached to the tops of hotel tables, toplate glass windows, etc. and to reflectors of lamps.

The nickel wire wound with enamelled wire is very convenient, and isconvenientlyused doubled so-as to form a complete magnetic circuit. InFig. 2 the steel sounding board and steel pins complete the magneticcircuit.

Where a stringed instrument is used as in Fig. 2 means may be attachedfor changing the natural resonant periods simultaneously,

by means well known inthe art. It is advantageous as has been found byapplicant, to pick up violin music by a violin used as pick up, and touse a violin as loud speaker, and to use pianos for piano music, thoughthis is not" essential as apiano loud-speaker 'will reproduce voice andviolin with aston ishing fidelity. Applicant having discovered that,contrary to the heretofore universally accepted doctrine, consonants, aswell as vowels, can be perfectly transmitted and reproduced, by thismeans, by these instrument-s. Many other uses of the devices shewn willsuggest themselves.

It. will be noted that the method herein described and claimed isfundamentally different from any of the previously known methods ofutilizing magnetostriction. In the previous methods the magnetism of thecore when altered by a mechanical strain only gave one single impulsecorresponding to that ma etic strain and if the magnetic strain was ept,on for an hour there would be no further electrical impulse producedbeyond that occurring during the fraction of a second while themechanical strain was being applied. Also the energy of the electricalimpulse produced was necessarily only a fraction of the energy of themechanical stress applied. In applicants method the change inpermeability produced by the mechanical strain permanently affects, solong as it continues, the flow of a fluctuating or alternating currentin the electrical circuit linked with the fe'rro-magnetic cone.Consequently the variation in the energy delivered by the alternatingcurrent persists so long as the mechanical strain is maintained, i. e.electrical impulses are continually produced for it may be hours, solong as the core continues: strained.

-Also the effect is or may be many millions of times greater because inapplicants method the energy is not derived from the mechanical stressbut from the energy of the alternating current circuit, the mechanicalstress merely acting as a throttler or valve turner to govern ordetermine the amount of the alternating current energy flowing throughthe circuit.

Applicant has found that a much'increased effect is obtained by makingthe magnetic core above described out of a single elongated crystal offerro-magnetic material, both when used as a receiver and as atransmitter, and as a generator, Hi; this is not claimed herein as it isclaimed and more fully described in another application.

tions comprising normally balanced electrical circmt, means for.impresslng upon the balanced sections of said circuit alternatingcurrent of a suitable frequency, means for unbalancing said circuit byvarying the permeability of a magnetic core forming a part of onebalanced section by the mechanical forces exerted on said core, andmeans. associated with said circuit for transmitting said electr calimpulse.

2. A circuit for transmitting electrical impulses in accordance withmechanical vanations comprising a normally balanced electrical circuit,means for impressing upon the balanced sections of said circuitalternating current of a suitable frequency, means for unbalancing saidcircuit by varying the perineability of a ferro-lnagnetic core forming apart of one balanced section by the mechanical forces exerted on saidcore, and means associated with said circuit for transmitting saidelectrical impulse.

3. A circuit for transmitting electrical impulses in accordance withmechanical variations comprising a pair of normally balanced shuntcircuits, at least one having a sound responsive current varying device,means for impressing a suitable alternating carrier current upon saidshunt circuits, a transformer having balanced primary windings connectedone in each shunt circuit and the secondary connected in circuit totransmit electric impulses corresponding to the mechanical variations ofthe sound responsive device.

4. A circuit for transmitting electrical impulses in accordance withmechanical variations comprising a pair of normally balanced shuntcircuits, a transformer havlng a pluwhose permeability is varied by theaction of the sound Waves on the diaphragms, and a normally balancedcircuit including said sound responsive device and a local alternatingcarrier current supply whereby the action of said sound responsivedevice will modulate said carrier current supply in accordancetherewith.

8. Means for transmitting compressional Waves, including a casing havinga diaphragm at opposite sides, a ferro-magnetic core adapted to receivemechanical stresses correspond-- ing to the compressional waves actingon said diaphragm, and means operated thereby for modulating a localcarrier source in accordance with the compressional waves.

REGINALD A. FESSENDEN.

rality of primary windings connected in series in said shunt circuitsand a secondary for transmlttlng the electric lmpulses, means forimpressing an alternating current on the balanced circuit and meansincluded in one of said shuntcircuits for unbalancing said circuitcomprising a sound responsive current varying device having aferro-magnetic core connected in said circuit.

5. A circuit for amplifying compressional wave impulses, including anelectromagnetic sound responsive device having a ferro-magnetic corewhose permeability varies in accordance with the compressional Wavesimpressed on the sound responsive device, a

ing the permeability of oneof them in accordance with the compressionalWaves, and means for transmitting the unbalanced component of theelectric Wave.

7. Means for transmitting compressional wave impulses, including a soundresponsive device having a pair of diaphragms responsive to sound waves,a ferro-magnetic core

